title: Neuropeptide Y mediates orexin A-mediated suppression of pulsatile gonadotropin-releasing hormone secretion in ovariectomized rats.
abstract: OBJECTIVE
  Reproductive functions are influenced by various feeding regulators. Orexin, which is one of orexinergic peptides, suppresses the pulsatile secretion of luteinizing hormone (LH) in bilaterally ovariectomized (OVX) rats. However, the mechanism of this effect is still not clear. To investigate whether neuropeptide Y (NPY) is involved in the orexin A-mediated suppression of pulsatile LH secretion, we evaluated the effects of NPY antibody on the suppressive effect of orexin A.
  
  
  METHODS
  Orexin A was administered intracerebroventricularly (icv) and NPY antibody (NPY-Ab) was injected before icv administration of orexin A in OVX rats. Pulsatile LH secretion was analyzed by measuring serum LH concentrations in the next 2 h in blood samples drawn at 6-min intervals by radioimmunoassay.
  
  
  RESULTS
  Administration of orexin A significantly reduced the mean LH concentration and LH pulse frequency. Co-administration of NPY antibody with orexin A significantly restored the suppressive effect of orexin A on the mean LH concentration and LH pulse frequency.
  
  
  CONCLUSIONS
  NPY mediated the suppressive effect of intracerebroventricularly injected orexin A on pulsatile LH secretion, suggesting that hypothalamic orexin suppressed pulsatile gonadotropin-releasing hormone (GnRH) secretion via NPY in the hypothalamus of female rats.
authors.affiliation: Department of Obstetrics and Gynecology, Institute of Health Biosciences, University of Tokushima Graduate School, Tokushima, Japan.
authors.forename: Machiko
authors.initials: M
authors.lastname: Kiyokawa
authors.forename: Toshiya
authors.initials: T
authors.lastname: Matsuzaki
authors.forename: Takeshi
authors.initials: T
authors.lastname: Iwasa
authors.forename: Rie
authors.initials: R
authors.lastname: Ogata
authors.forename: Masahiro
authors.initials: M
authors.lastname: Murakami
authors.forename: Riyo
authors.initials: R
authors.lastname: Kinouchi
authors.forename: Shinobu
authors.initials: S
authors.lastname: Yoshida
authors.forename: Akira
authors.initials: A
authors.lastname: Kuwahara
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Yasui
authors.forename: Minoru
authors.initials: M
authors.lastname: Irahara
mesh_terms: D000818:Animals; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000097:blood / Q000378:metabolism*; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism; D007276:Injections, Intraventricular; D047908:Intracellular Signaling Peptides and Proteins / Q000008:administration & dosage*; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism; D009478:Neuropeptide Y / Q000037:antagonists & inhibitors / Q000502:physiology*; D009479:Neuropeptides / Q000008:administration & dosage*; D000068797:Orexins; D010052:Ovariectomy; D051381:Rats; D017208:Rats, Wistar
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D009478:Neuropeptide Y; D009479:Neuropeptides; D000068797:Orexins; D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone